Spark Plug Issue

[speedracer]

My 79 Spider started stumbling on acceleration recently, and then she wouldn't start at all. Thankfully she was in the garage when she didn't start.

I checked for fuel flow and I saw that the carb was getting fuel, so I pulled a spark plug, and lo and behold, the 4 part prong (electrode?) at the top of the plug was almost completely gone, burned down to nubs. I pulled the other 3, and I found the same thing. These plugs were the gimmicky 4 prong Lodge Golden with only a few thousand miles on them. The car was running very good before this problem, and since I just replaced the plugs with Champions, she is running fine again, but there could still be a problem.

Cheap plugs? Is the spark to hot? Is it to lean or to rich? My guess is to lean, but there is no pinging, knocking or dieseling. Bad timing?

What say the experts?

[131]

What plugs are you running? Need more information than a brand name. I've only ever run NGK BP6ES in my Fiat motors. We did have a customer with a 1600 pushrod motor that was burning oil and fouling plugs, we tried BP5ES, a bit hotter, to try burning the oil off, but the centre electrode burnt away.

[So Cal Mark]

if the catalyst is plugged, you'll burn the tips right off the plugs

[speedracer]

The cat is long gone Mark.

I don't know the number of the old plugs, just that they were Golden Lodge, 4 prong style. I've heard some bad things about the 4 prong styles. Could they have been a problem? The Champion plugs I just installed are Copper Plus 415/RN9YC, single prong. That's what the part's book called for on a 79 Spider.

[azruss]

I have had good luck with dual pronged plug in an old motor with leaky valve seals. Helped fouling issues. I bought some Golden Lodge plugs but replaced them when i went with Mark's dizzyless ingnition that required a much large spark gap than i could achieve with the 4 prong plugs. With past Fiats, i found Champions to run the best.

[majicwrench]

Don't overthink it, get rid of those oddball plugs.

[speedracer]

Don't overthink it, get rid of those oddball plugs.

I like the way you think.

I took her out for a nice ride today and she felt great. I'll pull a plug after a few hundred miles and see how they look.

[divace73]

just to add my 2c worth to this, I bought the Bosch 4 prong plug about 10+ years ago and haven't had an issue with them...unless of course I change them out for something else to see if there is a difference????

[DanD]

The electronic ignition on a 79 puts out a way hotter spark than anything available when those plugs were designed.

[Kevin1]

Every time I have ventured into the "better" spark plug experiment for the Fiat I have always come back to Bosch or Autolite, single electrode, boring old vanilla plugs. They seem to work best, at least in my car.

[speedracer]

just to add my 2c worth to this, I bought the Bosch 4 prong plug about 10+ years ago and haven't had an issue with them...unless of course I change them out for something else to see if there is a difference????

You might want to check them.

My car ran fine until my last ride, when she started hesitating close to home. So I parked it and then it wouldn't start. The end for these plugs came quickly. How the car was running at all was amazing.

I will say though, that the car seemed to be a hair more responsive and even a bit louder through the exhaust with the old plugs. Somehow, the car seems tamer with the Champions. Perception, or real?

[speedracer]

The electronic ignition on a 79 puts out a way hotter spark than anything available when those plugs were designed.

Hmmm, I had no idea.

That would explain why they were so burned-up then.

So are the Champion's that the parts book called for good for this car, or will I wind up with the same problem

[majicwrench]

Like Honest Abe said, don't believe everything you read on the internet. Or on this forum

The electronic ignition on a 79 does not put out much more than the points system.

And regardless of system, it will only produce enough voltage to jump the gap. If you gap plugs at .020, even the most high zoot system will only produce enough voltage to jump gap.

Which is why, on a high zoot system, you can run a larger gap, because it will produce the 50k volts needed to jump big gap.

Newsflash, high zoot systems don't cause plugs to fail.

Quit overthinking this and run stock plugs.

I like NGK, but Autolite, Champion, Bosch, they all work.